I would think about getting a piece of foam core board, either black or white depending on the subject, and using that as the background. Needs more contrast. Another tip you might want to consider is to not center everything. And maybe try the shot in both hor'z and vert.

Personally, I like the theme as such, however I don't like that there's soooo much room around the dead flower, so harsh light, overexposure in many parts, very little contrast, and the subject out of focus. If the flower is the subject, why is part of the concrete to its left plus the bottom part of the leaves in focus?